The recent devastating tornado outbreak in Alabama raises concerns about building codes. The fact is, several of the Alabama tornadoes were EF4 (166-200 mph) or EF5 (200 mph or more( and it is simply too cost-prohibitive to design regular homes to be able to withstand such forces.
However, 98 per cent of all tornadoes produce damage in the EF0 (65-85 mph), EF1 (86-110 mph), EF2 (111-135 mph) or EF3 (136-165 mph) range. There are things builders can do to make houses reasonably safe from these winds, particularly EF2 and below, which is the most common. Houses that explode in a tornado do so not because of pressure, but because the roof is blown off and the walls fall down. In a well-built home, joists are attached to the walls with steel joist hangers instead of a single nail, and the walls are attached to the foundation with heavy anchor bolts.
Such homes will sustain damage in a tornado, but should avoid total destruction in all but the worst of storms